The present invention relates to a hybrid integrated circuit device and manufacturing method thereof, and more particularly to a hybrid integrated circuit device having a resin seal body formed on a hybrid integrated circuit substrate by transfer molding and to a manufacturing method thereof.
Generally, there are, principally, two methods of sealing employed for hybrid integrated circuit devices.
The first method employs member having such a form as placing a lid, generally called a case member, on a hybrid integrated circuit substrate mounted with circuit elements of semiconductor chips or the like. This structure includes a hollow structure or that having a resin separately filled therein.
The second method is injection molding as a process to mold semiconductor ICs. This is described, e.g. in Japanese Patent Publication No. H11-330317. The injection molding generally uses thermoplastic resin. For example, the resin heated at 300° C. is injected under a high injection pressure and poured into a mold at one time, whereby the resin is molded. Since a resin polymerization time is not required after pouring a resin into a mold, there is a merit to shorten the operation time as compared with transfer molding.
Explanation will be made on a method of manufacturing a conventional hybrid integrated circuit device using injection molding, with reference to FIGS. 13 to 16C.
First, an aluminum (hereinafter, referred to as Al) substrate 1 is employed as a metal substrate as shown in FIG. 13, in order for explanation.
The Al substrate 1 is anodized in its surface. Furthermore, a resin 2 having an excellent insulation property is formed on the entire surface of the anodized Al substrate 1. However, the oxide may be omitted where voltage resistance is not taken into consideration.
On the resin 2, a conductive path 3a is formed by a Cu foil 3. On the conductive path 3a, an active element 5 such as a power transistor, transistor or IC, and a passive element 36 such as a chip resistor or chip capacitor, are mounted through a solder 40. Thus, a predetermined circuit is realized. Herein, by providing electrical connection using an Ag paste or the like, soldering may be partly omitted. In the case of mounting face up an active element 5, such as a semiconductor chip, connection is through a metal fine wire 7 formed by bonding. Further, an outer lead 8 is connected with an external electrode terminal 11 and is exposed from the resin sial body 10 to exterior.
Herein, the thermoplastic resin adopted is a resin called PPS (polyphenyl sulfide).
The injection temperature of thermoplastic resin is as high as 300° C. Consequently, there is a problem that solder 12 be fused by the hot resin thereby causing poor soldering. For this reason, an overcoat 9 is formed by potting a thermosetting resin (e.g. epoxy resin) in a manner previously covering solder joints, metal fine wires 7, active elements 5 and passive elements 6. Due to this, the fine wires (approximately 30-80 μm) particularly are prevented from being fallen down and broken under an injection resin pressure during forming with a thermoplastic resin.
As shown in FIGS. 16B and 16C, a resin seal body 10 is formed by a support member 10a and a thermoplastic resin. Namely, a substrate 1 mounted on the support member 10a is covered with thermoplastic resin by injection molding. The support member 10a and the thermoplastic resin have an abutment region. The abutment region of support member 10a is fused by the poured hot thermoplastic resin, thereby realizing a full-mold structure as shown in FIG. 13.
Next, explanation will be made on a conventional method of manufacturing a hybrid integrated circuit device using injection molding, with reference to FIGS. 14 to 16C.
FIG. 14 is a flowchart, including a metal substrate preparing process, an insulating layer forming process, a Cu foil pressure-laying process, a partial Ni plating process, a Cu foil etching process, a die bonding process, a wire bonding process, a potting process, a lead connection process, a support member attaching process, an injection mold process and a lead cutting process.
FIGS. 15A to 16C show the sectional views of the processes. Note that the processes, that are apparent without showing, are omittedly shown.
At first, FIGS. 15A and 15B show a metal substrate preparing process, an insulating layer forming process, a Cu foil pressure-laying process, a partial Ni plating process and a Cu foil etching process.
In the metal substrate preparing process, prepared is a substrate in consideration of its property of heat dissipation, substrate strength, substrate shield and the like. This example uses an Al substrate 1 having a thickness, e.g. of approximately 1.5 mm, excellent in heat dissipation property.
Next, a resin 2 excellent in insulation property is further formed over the entire surface of the aluminum substrate 1. On the insulating resin 2, a Cu conductor foil 3 is pressure-laid to constitute a hybrid integrated circuit. On the Cu foil 3, an Ni plating 4 is provided over the entire surface in consideration of adhesion to a metal fine wire 7 electrically connecting between the Cu foil 3 as a lead-out electrode and an active element 5.
Thereafter, a known screen-printing is used to form Ni plating 4a and a conductive path 3a. 
Next, FIG. 15C shows a die bonding process and a wire bonding process.
On the conductive path 3a formed in the preceding process, an active element 5 and a passive element 6 are mounted through a conductive paste such as a solder paste 12, thereby realizing a predetermined circuit.
Next, FIGS. 16A and 16B show a potting process, a lead connection process and a support member attaching process.
As shown in FIG. 16A, in the potting process, prior to a later injection mold process, potting is previously made with a thermosetting resin (e.g. epoxy resin) onto the solder junctions, metal fine wires 7, active elements 5 and passive elements 6, thereby forming an overcoat 9.
Next, prepared is an outer lead 8 for outputting and inputting signals from and to the hybrid integrated circuit. Thereafter, the outer lead 8 is connected to the external connection terminal 11 formed in a peripheral area of the substrate 1 through a solder 12.
Next, as shown in FIG. 16B, the hybrid integrated circuit substrate 1 connected with the outer lead 8 and the like is mounted on a support member 10a. By mounting the substrate 1 on the support member 10a, it is possible to secure a thickness of a resin seal body at a backside of the substrate 1 during injection molding as explained in the next process.
Next, FIG. 16C shows an injection mold process and a lead cutting process.
As shown in the figure, after potting is done with a thermosetting resin on the substrate 1 to form a overcoat 9, a resin seal body 10 is formed by injection molding. At this time, in the abutment region between the support member 10a and the thermoplastic resin, the abutment region of the support member 10a is fused by the injected hot thermoplastic resin and turned into a full-mold structured resin seal body 10.
Finally, the outer lead 8 is cut to a use purpose thereby adjusting the length of the outer lead 8.
By the above process, a hybrid integrated circuit device is completed as shown in FIG. 13.
On the other hand, in the semiconductor industry, it is a general practice to carry out a transfer mold process. In a hybrid integrated circuit device by the conventional transfer molding, a semiconductor chip is fixed on a leadframe, e.g. of Cu. The semiconductor chip and the lead are electrically connected through a gold wire (hereinafter, referred to as Au). This is because the impossibility of employing an Al fine wire in respect of its less elasticity and ready bendability and time-consumed bonding requiring ultrasonic waves. Consequently, there has not conventionally existed a hybrid integrated circuit device that is formed by one metal plate to have a circuit formed thereon and further the substrate wire-bonded by Al fine wires is directly transfer-molded. Further, as well as a printed circuit board and a ceramic substrate, there has not conventionally existed a hybrid integrated circuit device having a substrate wire-bonded by Al fine wires directly transfer-molded.
As shown in FIG. 13, in the conventional hybrid integrated circuit device formed by transfer molding, a resin seal body 10 is formed by injection molding after a hybrid integrated circuit substrate 1 is mounted on a support member 10a. Consequently, the insulating region at the below of the substrate 1 can be easily controlled to a thickness of approximately 0.5-1.0 mm, for example. Meanwhile, because the resin seal body 10 is formed after placing the substrate 1 on the support member 10a, it is not problematic whether the substrate 1 is punched out at the main surface or back surface.
However, when a resin seal body is directly formed over the hybrid integrated circuit substrate by transfer molding, there are cases that the burr formed is broken during transfer molding at a time of punching out the substrate. The fragments of burr will be contained in a resin seal body formed at the below of the substrate. Due to this, circuit voltage is applied onto the substrate, a high voltage of which is to be applied to the resin seal body at the below of the substrate. Thus, there has been a problem that the reliability on voltage resistance is unavailable on the resin seal body containing substrate burrs.
Furthermore, in a hybrid integrated circuit device of a injection mold type, there is a need to prevent a metal fine wire 7 from being bent or broken under an injection pressure upon molding, or to prevent a solder 12 from flowing at the temperature during injection molding. For this reason, the conventional structure shown FIG. 13 has adopted a potted overcoat 9 in order to cope with the above problem.
However, potting is made with a thermosetting resin (e.g. epoxy resin) to form an overcoat 9, and thereafter injection molding is carried out. Accordingly, there is a problem of requiring material and operation cost in concerned with such thermosetting resin.
Meanwhile, in the conventional hybrid integrated circuit device by transfer molding, a semiconductor chip or the like is fixed on an island. Although the heat generated by the semiconductor chip or the like dissipates through a fixing region, there has been a problem that there is restriction in heat dissipation area thus resulting in poor heat dissipation.
Furthermore, as noted above, the Al fine wire is readily bent due to the causes of being ultrasonically bonded to have a weak neck and further less resistive to resin injection pressure because of its low elastic modulus. For this reason, it is a practice to use, as a metal fine wire, an Au wire resistive to resin injection pressure in the wire-bonding for a resin seal body. The transfer molding employing an Al wire is not in the current practice. It is, therefore, a problem of the present invention to provide a structure and manufacturing method realizing the transfer molding free from bending by actively employing such an Al fine wire.